Trichomonas vaginalis, causes one of the most common sexually transmitted disease in humans, trichomoniasis. Trichomoniasis is a serious disease that causes flagrant vaginitis and has been linked to infertility, preterm delivery, low birth weight infants, cervical cancer and markedly increased susceptibility to HIV. Cell surface glycoconjugates appear to mediate parasite binding to host cells. An in vitro culture system of human vaginal epithelial cells (HVECs), which exhibits parasite-host specificity, has been developed. Exposure of HVECs to parasites results in destruction of HVECs within 30 h. Periodate treated parasites do not damage HVECs. T. vaginalis possesses a cell surface glycoconjugate, lipophosphoglycan (LPG), which displaces parasites binding to HVECs, implying a specific receptor-ligand interaction. A related water soluble glycan (TV-SG), released by parasites, has also been purified. The long term goal of this proposal is to elucidate the mechanism(s) of T. vaginalis pathobiology on a molecular and cellular level. The specific aims are: 1) to utilize the HVEC culture system and an 35S-methionine-labeled-parasite binding-displacement assay to study the role of LPG in host-parasite adhesion, and to identify and purify "receptor" molecules on the HVEC surface that bind parasites. 2) to complete the structural characterization of LPG and study its relationship to TV-SG; with the expectation that structural analysis will be correlated with bioactivity. The binding assay will also be employed to assay portions of the LPG molecule derived by chemical and enzymatic treatments. 3) Parasite cytotoxicity toward HVECs will be studied by quantitative assays and contact-dependent and contact-independent mechanisms will be evaluated. HVEC destruction will be assayed for necrosis vs. apoptosis using an ELISA assay. Receptor purification will be based on either a panning technique to search for radiolabeled HVEC surface molecules that bind to LPG or an affinity column approach with immobilized LPG. LPG structure will be characterized using a variety of techniques, including HPLC, Glyko-FACE, MALDI-TOF MS and NMR. These studies will help to define the mechanisms of T. vaginalis pathogenicity, which will ultimately lead to better treatments for trichomoniasis.